For purposes of preventing excessive pronation and supination of the foot occuring in walking and running, a conventional sports shoe includes a heel counter consisting of a board of synthetic resin or resin-impregnated leather and inserted between an upper and a lining at the periphery of the heel portion of the shoe, and a stabilizer having a reinforcing wall positioned on the side of the heel portion to reinforce the heel counter.
The stabilizer 19 has a particular shape for one of various shoes as shown in FIG. 12 of the accompanying drawings and, therefore, it has been found that, due to individual differences, the stabilizer fits the heel of one wearer but does not fit the heel of the other wearer. In the former case, the stabilizer can firmly and stably hold the heel of the foot during running because of stiffness of resin from which the stabilizer is formed, thereby preventing rolling of the heel. In the latter case, however, the heel of the foot is unstable in the shoe and the wearer might have a shoe sore caused by touching the stabilizer having a relatively high stiffness. The wearer might also suddenly sprain the ankle of the foot and be subject to impedimenta to the ankle, knee, waist and the like after a prolonged use of the shoe.
For purposes of fitness of the heel portion of the shoe, it has been known to employ a cup-like stabilizer shaped curvedly from a heel-treading portion toward a reinforcing wall thereof to conform to the shape of the heel. This can attain a certain degree of improvement in fitness but still makes it impossible to accommodate the individual differences so that more complete stability of the heel can not be accomplished.
Japanese patent public disclosure Sho 50-1855 and Japanese patent public disclosure Heisei 4-117903 disclose sports shoes each employing bouncing putty plastically deformed easily when a stress is applied more slowly and exhibiting a high degree of bounce under suddenly applied stresses in order to further improve the fitness of the heel portion of the shoe.
In the invention described in each of the publications, the bouncing putty is contained in a pad adhesively secured to a midsole of soft elastic material and a soft upper. With this arrangement, pressure from the heel of a wearer is liable to escape through the pad to the midsole and the upper so that the pad can not be plastically deformed enough to conform to the shape of the heel. This makes it impossible to effect full action of the bouncing putty for good fitness.
The bouncing putty itself has no self-supporting capability and a high specific gravity. Japanese patent public disclosure Heisei 4-117903 teaches mixing bouncing putty with micro-balloons in order to eliminate these disadvantages. However, the process is complicated and a significant number of micro-balloons to be mixed in the bouncing putty is required to attain a good self-supporting capability. This will lead to a high cost of the material.